1. Field of the Invention
The invention concerns a device conventionally referred to a xe2x80x9ccookerxe2x80x9d for the thermal processing of materials for the production of sugar-containing or confectionary products.
The essential components of such materials include sugar or sugar substitutes of various types in mixture with other nutrients and culinary additives such as starches, lactose products, gelatinizers and the like. Depending upon the type of material, the thermal treatment may be any of heating, solublizing and/or cooking, and the requirements for the thermal treatment can vary greatly depending on the type of the material to be treated. Many materials contain components which are liable to burn during heating, or which must be handled with thermal sensitivity. This applies, for example, to milk or milk components, fruit components or gelatinizing agents such as gelatin, starches, pectin, and gum arabicum.
2. Description of the Related Art
There are many types of cookers, which are, however, as a whole, not satisfactory in all respects. The oldest type are the so-called salt cookers (a type of heated kettle), which often were equipped with stirrers and were satisfactory for the batch-wise treatment of simple, less sensitive materials. However, as soon as the materials were used which were liable to burn, there were problems. It helped in part to provide the stirrers with scrapers (xe2x80x9cscraped heating surfacesxe2x80x9d). Besides this, continuous processes were not possible with these cookers.
For a continuous processing, the so-called coiled pipe cookers have been in use even until today. In the coiled pipe cooker, the material to be treated flows through a coiled pipe, which is heated from outside by a heating medium. Various attempts have been made to overcome this problem, including, for example, a flattening of the cross-section of the coiled pipes for increasing the velocity of the material flowing through the coil pipe in the wall area, so it is by these measures that the contact time between the material and the heating surface is kept as small as possible.
The success of this type of measure is, however, limited, and the cooker must frequently be turned off for cleaning. Many substances, in particular those based on starch, could not be satisfactory processed at all. For these substances, until now the so-called jet-cookers have been preffered, in which super heated steam is injected directly into the substances. The advantage of this process is the relatively simple technical application, and the fact that no heating surface is present onto which the substance can burn. The disadvantages include the direct contact between the heating medium and the substance.
In recent times, a cooker type has become known, which operates on the principle of a tubular heat exchanger and is described, for example, in DE-C 35 28 426. In this cooker, a tube bundle of a longitudinally extending tubular heat exchangers is flowed through by a heating medium, while the substance to be treated flows around the outside of the tubes within the jacket of the heat exchanger. It is forced in a flow path running essentially perpendicular to the pipes of the pipe bundle via baffles or deflection plates, which extend in the inner space of the thermal exchanger and are passed through by the tubes of the tube bundle, and, thereby, experience a supplemental agitation or mixing. This results in a good energy transference, which is possible due to the application of a low temperature difference between the substance and the heating medium, with the consequence, that a tendency towards burning is minimized, and the product quality is improved.
During the heating or, as the case may be, cooking of a product which has a tendency to burn, there forms with all conventional continuous cookers, without scraped heating surfaces, a depositing of product upon the heating surfaces. The layer thickness of this deposited product increases with the passage of time, whereby the thermal transference from heating medium to product is reduced. In order to maintain the desired product temperature, as constant as possible, the temperature of the heating medium must be increased, whereby the burning effect is further accelerated. Further, these burned deposits lead to the risk of a release of burned particles, which become distributed throughout the product. During the use of thermally liable products, at least partial thermal decomposition of these products occurs, which can become apparent as discoloration, and which is partially compensated with overdosing. All of these are better avoided using the cooker described in DE-C 35 28 426 than with the conventional types of cookers.
This known cooker exhibits problems, which can be traced back in particular to the baffles or deflection plates. These deflection plates mainly define flow chambers running between them perpendicular to the tubes in such an arrangement, that the material sequentially flows through a ring shaped gap between the one deflection plate and the inner wall of the cooker, and then through a central opening in the next deflection plate, that is, practically from the edge zone of the cooker to the center, and then again to the edge zone, etc. Further, there exists in the introduction and withdrawal areas of the substance, zones without forced flow-through, that is, in these areas material can reside for indeterminate lengths, so the occurrence of burning is possible. Further, the steam conducting pipes in the area of the central opening of the deflection plates are in part not flowed-by perpendicularly, but rather in the direction longitudinal to these pipes, whereby in these areas the material is not subject to turbulence and mixing. As a practical matter, as a result of design, there are exit zones at the deflection plates with edge recesses or perforations in the area of the central axis between the steam conducting pipes which are not flowed through.
With the present invention, these problems are to be avoided and the technology is to be provided with a cooker which is optimally suited for all possible types of materials to be treated.
Beginning with a cooker in the form of a tubular heat exchanger, in which tubes in a bundle extend longitudinally within a jacket housing, and are individually flown through by a heating material, and in which the material to be treated is introduced and withdrawn via pipe fittings along the jacket sides, which material to be treated flows over the outside of these tubes, wherein deflection plates are provided within the jacket, which plates define flow chambers and which include openings for the transition of the material to be treated from one flow chamber to the next, it is inventively provided that the baffle plates are provided along one narrow edge area with segment-like openings and that these openings are located alternating on diametrically opposite sides of the inner walls of the jacket housing, wherein in the flow direction, the opening of the first deflection plate lies opposite to the introduction fitting for the material, and the opening of the last deflection plate lies opposite the withdrawal fitting.
In accordance with the invention, it is achieved in constructively simple, however, extraordinarily effective manner, that the material to be treated is directed along a zigzag flow path perpendicular to the heating pipes, and that there are no areas in which partial flows or side currents can break out and be delayed somewhere with undetermined dwell time. Therewith, the material can flow within the chambers only perpendicularly to the heating pipes, never in parallel to the pipes. In combination with the conventional inherent advantages of a cooker operating on the principle of a tubular heat exchanger, an optimal result can now be guaranteed for practically any material to be treated, regardless of its composition. It is of course understood that the operating parameters of the cooker, such as temperature, pressure and flow-through speed, are to be adjusted in known manner for the material to be treated.